The present invention relates to the field of diagnostic methods. Specifically, the present invention contemplates a method for diagnosing a liver disease in a subject and a method of differentiating between NASH and NAFLD. The invention also relates to tools for carrying out the aforementioned methods, such as diagnostic devices.
Fatty liver disease that develops in the absence of alcohol abuse is recognized increasingly as a major health burden, in particular if an inflammatory component is involved such as in non-alcoholic steatohepatitis (NASH). Estimates based on imaging and biopsy studies suggest that about 20% to 30% of adults in the United States and other Western countries have excess fat accumulation in the liver. About 10% of these individuals, or fully 2% to 3% of adults, are estimated to meet current diagnostic criteria for NASH. Sustained liver injury leads to progressive fibrosis and cirrhosis in about 30% of NASH patients. The diagnostic criteria for NASH continue to evolve and rely on the histologic findings of steatosis, hepatocellular injury (ballooning, Mallory bodies), and the pattern of fibrosis.
Liver biopsy has remained the criterion standard or “gold standard” in the evaluation of the etiology and extent of disease of the liver such as non-alcoholic fatty liver disease (NAFLD) and NASH. Percutaneous liver biopsy is the preferred method to determine NAFLD and to differentiate NASH from NAFLD. Other biopsy methods are typically even more invasive and include transvenous and laparoscopic liver biopsy. The American Gastroenterological Association has published detailed recommendations on how to grade NAFLD comprising NASH into macrovescicular steatosis grades, necroinflammatory activity grades and fibrosis stages (American Gastroenterological Association 2002, Gastroenterology 123: 1705-25; Brunt 1999, Am J Gastroenterol. 94: 2467-74, Brunt 2010, Nat Rev Gastroenterol Hepatol. 7:195-203).
Although liver biopsies are generally regarded as safe, they bare risks that are potentially lethal. Almost two thirds of complications of liver biopsy occur within two hours. Approximately 2% of patients undergoing liver biopsy require hospitalization for the management of an adverse event. Significant bleeding after a liver biopsy occurs in approximately 1% of patients who are biopsied. If bleeding persists, a blood transfusion may be needed. Surgery or angiography, where the bleeding site is identified and treated, may be required if the bleeding is severe or does not stop on its own. Intraperitoneal hemorrhage is the most serious consequence of bleeding. Fatal complications have been reported in up to 0.04% of biopsied patients.
An additional challenge for the liver biopsy is the cost associated with the diagnosis. The costs for liver biopsy and histological assessment were estimated to be above USD 1000 for needle biopsies without complications and above USD 2700 with complications. Moreover, biopsy assessment of the type and severity of hepatic steatosis is associated with a significant time investment for the practitioner and the patient for examination and post-biopsy care.
Metabolite biomarker based methods which either analyze blood or tissue samples have been recently reported for diagnosing fatty liver diseases; see WO 2009/059150 and WO 2010/018165. Other biomarkers, such as lipids, noninvasive imaging or scoring systems are also known and are described, e.g., in Vuppalanchi 2009, Hepatology, 49:306-317; Pun 2007, Hepatology 46:1081-1090.
Thus, a robust minimal invasive test to reliably and efficiently diagnose NASH and differentiate the inflammatory indication NASH from the less harmful NAFLD without inflammatory component is needed.